The mage can hear sounds on subsonic or supersonic frequencies that the human ear cannot normally distinguish, but this spell does not improve her hearing ability (it adds no dice, but does extend the range of sounds she can hear).
A Wits + Composure roll is made for the mage to discern high-frequency sounds (a dog whistle) or low-frequency sounds (the rumble of a distant herd of elephants). Sounds that are very high or low on the scale from the normal human range of hearing might impose dice penalties.
Guardians of the Veil Rote: Thunderous Whispers
Perception is a large part of being a Guardian of the Veil.
A number of Guardians make use of this rote to pick up on things ordinary humans might miss. After all, the world is full of all sorts of wondrous and terrible phenomena, and one never knows if, say, all the dogs in the neighborhood are howling because of some unnatural presence, or due to nothing more than a sound painful to their ears, one far above the register audible to humans. Mages of the Mysterium also make use of such magics, for sometimes the secret to an enigma lies not in what one can see, but in what one can hear.